1. Field of the Invention
The present invention relates to a display apparatus obtained by arranging a plurality of organic light-emitting devices (organic electroluminescent (EL) devices) on a substrate. In particular, the present invention relates to a display apparatus with improved dependency of a view angle.
2. Related Background Art
In recent years, a display using an organic electroluminescent device (hereinafter referred to as the “organic EL device”), which serves as a display apparatus replacing a liquid-crystal display, has been attracting attention. Applied research for forming the display into a device including the development of a material has been vigorously performed because of various advantages of spontaneously emitting light, requiring no backlight, increasing in the area of the display with ease, providing desired colors by using various materials, driving at a low voltage, and being excellent in high-speed responsiveness.
Further, the display has been recently becoming widespread in the market in the form of a next-generation display such as: the sub-display of a mobile phone; an on-vehicle display; or the display of a digital camera.
An organic EL device is a carrier injection-type flat light-emitting device utilizing light emission occurring upon recombination of an electron and a hole that have reached a light emission layer. FIG. 8 is a schematic diagram showing the general constitution of an organic EL device. The organic EL device shown in FIG. 8 is constituted by: forming a transparent electrode 13 to serve as an anode on a transparent substrate 14; stacking an organic compound layer 12 including a light emission layer on the transparent electrode 13; and stacking a metal electrode 11 to serve as a cathode on the organic compound layer 12. The organic compound layer 12 may appropriately include an electron transport layer, a hole transport layer, or the like other than the light emission layer, depending on a purpose. In general, the organic compound layer 12 is a thin film having a thickness of about 100 nm. In FIG. 8, light generated in the light emission layer of the organic compound layer 12 is taken from the side of the substrate 14 through the transparent electrode 13.
In addition, FIG. 9 is a schematic diagram showing another general constitution of an organic EL device. The organic EL device shown in FIG. 9 is constituted by: forming a reflection electrode 23 on a substrate 24; forming an organic compound layer 22 including a light emission layer on the reflection electrode 23; and forming a transparent electrode 21 on the organic compound layer 22. Light generated in the light emission layer is taken to a side opposite to the substrate 24 through the transparent electrode 21.
As described above, an organic EL device is a spontaneous light-emitting device, is composed of a thin film having a thickness of about 100 nm, and has a reflection electrode. As a result, a so-called interference phenomenon in which light beams generated in the device strengthen or weaken each other occurs. Therefore, it is known that luminance and an emission spectrum vary depending on a view angle.
Such dependency of the view angle becomes a problem of reducing display quality, in view of application to a display apparatus. Japanese Patent No. 2843924 discloses a technique for solving such problem. According to Japanese Patent No. 2843924, an interference condition is set to a condition of weakening light beams mutually at the view angle 0° so that the dependency of luminance on the view angle is reduced.
However, the technique disclosed in Japanese Patent No. 2843924 has a problem that the luminance itself of the display apparatus is sacrificed although the technique exerts a certain effect of improving the dependency of the view angle.